Re: Re: Re: 18 inch tires on a Lexus SC400

First off, Tires ARE still comprised of rubber. Both natural and synthetic. Along with a lengthy list of other materials. The %age of "rubber" is different for different tires depending on what attributes and characteristics the manufacturer is striving for. The %age of "pure rubber" in a tire has decreased over the years with advancements in compounding and discovery of new "ingediants" to improve and enhance the performance. 45 psi is NOT the recomended pressure, nor is it on most tires. There is a huge difference between what "max" inflation pressure is for a tire and what "recomended" inflation pressure is. The max psi stamped or molded on the sidewall is just that - the maximum inflation pressure allowed for that tire. It comes from the Tire manufacturer. The recomended inflation pressure is equally as simple, it comes from the vehicle manufacturer and is what they recomend the tires should be inflated at ("cold" reading). There are several factors that are considered for this recomendation - Most impotantly is load capacity. There are set perameters for each size tire made as to how much wieght/load a tire can support and it is effected by each 1 psi change in pressure. Another factor is ride quality, at the hieghest level - the lower the psi the softer the ride the higher the psi the harder the ride. Though many other characteristics of the tire change as well, they would include but are not limited too: handling, braking, traction, acceleration, noise, etc., etc., etc.. they all improve/diminish or just change with any variance +/-. And 2psi increments can make a difference.The most common "max psi" stamping on a tire is 35 psi. As a general rule this would be found on "H" rated tires and below. 44psi and recently 51psi (not 45psi) can be found on higher performance rated tires. Again for several reasons - most impotantly load because the load on a tire increases when driven at higher speeds (something you wouldn't be able to expirience in your cadillac).Bottom line - once agian your information is inconsistant, and wrong. Not to mention continually distant from the original subject matter. As best I can tell; always related to letting everone know you drive a cadillac. If you haven't picked up on it so far - we don't care - unless of course someone asks a question related to driving one, then your comments MAY be relavant.